Oil return means for flooded evaporators



Jan. 15, 1935, J. ASKlN OIL RETURN MEANS FOR FLOODED EVAPORATORS FiledOct. 13, 1932 A w M 8? deaf/Ki Patented Jan. 15, 1935 1;. i

UNITED STATES PATENT OFFICE y on. RETURN Foe FL oonEn nvAPoRATons. n a

Joseph Askin, Buffalo, N. Y.', assignor'to readers J v ManufacturingCompany, Inc., Buffalo,

Application October 13, 932, Serial 'Nafss'mm.

M 6 Claims. (01-. 62- 126) This inventionrelatesto refrigerationevaporaity of tubes 11, and which is closed at one end by tors of theflooded, type such as are employed in a'platejl2-provided with an inletline 13 and a compressor-condenser-expander systems of mesuction line14. The inlet'line 13 passesthrough chanical refrigeratiomandit hasparticularrefa-boss 15, formed on the plate,-in which is mounterence tothe provision of means for effecting the ed, an inlet valve16,.theopening of which is con- 5 copious return of oil from theevaporatorto the ptrolled by a'pivoted'float member 17, in the formcompressor without concomitant return ofliquid .of an open cup orreceptaclei -A suctiontube 18, refrigerant; V f dependingintothe cavityof the cup 17, leads to It is wellunderstoodin the art that,-inthe typethe suction line 14,; 1 v a a y of refrigeration apparatus referred t o,oil tends The operation is that, asrefrigerant evaporates 10 toaccumulate in the evaporator, and some DIQ- in thecylinder 10, and,tubes 11, toproduce re- ,vision must be made for its return tothecomfrigeratiomthe liberated gases, together with such pressor, togetherwith gasified refrigerant. It is lubricant asthey may carry, fall intothe cup '17 likewise desirable to'prevent the return of liquid and arereturned to the compressor through the 515 refrigerant tothe compressonaslossesof operatsuction tube 18. Such evaporation lowers the 15 ingefficiency result if this condition occursl If liquid level in'theevaporator, thereby permitting the oil is returnedtoo-rapidly, however,the tenthe float 17, to drop open the valve 16, and admit dency to r urnrefri r n is au m nted whil -mixedliquid refrigerantiand lubricant 'tothe too slow an oil return rate is attempted the'reevaporator toreestablish the liquid level therein.

- a m y 106601116 il legg d, a d solesse ed As the oil is lighter thanthe refrigerant, it floats 20 -in its refrigerating capacity. Oillogging:,may on the surface thereof, and is carrie d into the take placein a system which operates satisfaccavity ofthe'float'during theevaporating action. -tori1y under certain conditions i 13 C Asstatedabove, a violent evaporating action .rtions be materiallychanged.IForeXampleQit'has may cause the injection ofglarge quantities of 2.25been noted that a domestic refrigerator operating liquid r fri rant i tth cup 1 7, hi h. i t .25

season.

P p y pp a y full capa ity may desired, while a very quiet action maynot cause becomeo l logged w it is j w b ry suificient disturbancetodischarge the oil into the li ht du y, as might be th ease y'w cup,thereby leading .to oil logging of the system. absent from the residence.during'; avaCatiOn To avoid both of these defects, this invention prof'vides for guarding the cavity of the cup from the 30 Thelpresentinvention provides for" thejreturn injectionof liquid refrigerant, andprovides means of oil in such copious quantities as to prevent oil forthe taking up, of 5 substantial volumes of the logging from thisor anyother cause, whilellimit- I oil floating on the're'frigerant surface.

ing the return of refrigerant toanor'malamount, 0 this gend, ,the cup 17is covered with a cover and thenin the form of gas, and it also providesplate 21, which shown as being in the form of I 35 a wick feed for oilreturn purposes which; exerts alid having,- turned under marginalportions 22,

a constanteffect on the, C Whiph it is'irnadapted-to engageoutwardly-[turned'flanges 23 mersed,, irrespective [of variations theyiq fid formed onthe cup itself. A s1ot 24, guarded by an level in t eevaporator! n Setting q b the p upwardly turned flange 25-, is formed atthe rear 0 p s of t v ti a 'ap i to Pra tice, fportion of. the lid21,-sothat the lid may be slid 4o erencewill be made to a typepfoil'return device I over the cup and 1 beyond the, tube 18. 'The inwhich an open cup iS adap QB lubriclearance between the flange; 25 andthe tube cant and refrigerant for return to the'compressor 1'8 provi des1 -an' input passage for directing the through a suctionlin e disposedinthe cup but it gases to the tube- 18 andit is additionally propor- 145will be understood that the'invention maybe em-' tioned to permit thebucket 17*to rise and fall bodied. in otherforms within the, purview,ofi the freely with the liquid level, so asnot to interfere following,claims. I i v with the action of the valve 16, but the gap is not Inthedrawing, Fig. l is a-transverse section .wide enough to provide forthe free passage. of through anevaporato-r header containing the inlargeamounts of liquid refrigerant which may vention; v r occasionally besplashed overthe rear portion 50 Fig; 2is a longitudin'al'section; and,of the cup and aroundlthe tube v18. 1

Fig. 3 is a perspective of a cupshown in Figs. v The plate 21 is:provided, at a number of point land 2. i 1 adjacent its margin, withnarrow slots or open- The evaporator is illustrated as comprising aings-t26, in which are disposed wicks 27, dipping ylind i l h 1l f -w isd n d a P m att their outer ends into the region ;-ofv .the oil i3layer in the evaporator, and terminating at their inner ends within thecavity of the float. These wicks may be made simply by folding fine meshcopper screen, say from eighty to two hundred mesh, on itself a numberof times, and then flattening the folds by a hammer blow or the like.

The size of the wicks is of some importance, and is readilyascertainable'for any given evaporator. Anne wick, :such as enemadeioftwo hundred mesh wire, does not feed oil from the supernatant layer intothe cup as rapidly as an eighty mesh wick of the same length and width,

However, a coarse mesh wick maybe so active .as to carry into the floatan appreciable amount of liquid refrigerant, and hence, in providing fora,

plurality of wicks, it is understood that mere "feeding capacity aloneis not contemplated, but the major purpose of using a large number ofwicks is to provide for high oil return capacitmwithout increasing therefrigerant return.

Inthe present device, it'has' been found that three or four wicks of onehundred mesh screen serve to return the oil as rapidly as itaccumulates, with practically no liquid refrigerant return. Thus, theuse of a number of slow feeding wicks is preferred to a s'ingle iast'feeding wick, since the former arrangement provides an enlargedevaporativ'e surface for the liquid refrigerant whichis occasionallycarried with the oil.

The lengthofthe exterior 'leg of the wick is, of course, constant, andits depth of immersion is determined for normal operating conditions bythe cup 17 :were fixed with respect to the shell 10. Such constructionis advantageous in preventing the return of liquid refrigerant throughthe wicks. A I i The apertures 26, through which the wicks 27 pass,preferably engage the wicks snugly, so that any liquidrefrigerant whichspreads out over the surface of the plate 21, and attempts to flowthrough the apertures, is taken up by the wicks, to be further retardedin its flow as liquid,--orto be taken up by the oil in the -wicks-and'sorendered ineil'ective to cause-backfrosting. fI'n operation,gasified refrigerant passes fromthe vapor space above the liquid levelsinto the cavity of the cup 17 and thence into thesuction tube 1-8,'-'flowing through the apertures which. are always open to it. Liquidrefrigerant, which maybe-splashed on the plate 21, is so impeded initsprogress that an opportunity is given to it to evaporate, and

hence practically no liquidrefrigeiant isadmitted to thereturn line.wicks, which, due to their nature'take upthe oil preferentially to theliquid refrigerant; and at such rate that the oilis returned practicallyas fast as it, collects. Oil may also bereturned through the openings inthe plate 21,"or with the .gasified refrigerant, which serves as acarrier for small oil particles.

The wicks 2'? may be of such size as to be automatically disengageablefrom the liquid in the header when the oil is drained therefrom, withthe object of preventing the withdrawal of pure liquid refrigerant fromthe header. This is. provided "for by the'difierencesin' specificgravity ofthe oil and the refrigerant, wherein normally the relativelylight oil floats on the refrigerant in a layer of approximately one halfinch, and, inasmuch as it affects the buoyancy on is rem-medby the saidtop being above the liquid in the evaporator,

of the float, it also affects the liquid level in the header, which isdependent upon the valve-controlling action of the float. Under theseconditions, which may be assumed to be normal, the float is deeplyimmersed in liquid, and, as a re- 5 sult the wicks enter the oil layer.However, in the absence of or during a substantial depletion of thelayer, the relatively heavier liquid refrigerant alone .afiects thebuoyancy of 'the float, which therefore floats more readily, and,through 10 its control of the valve, in effect lowers the liquid levelin the header. The wicks under this ,honditlon are withdrawn from theliquid until a substantial quantity of oil enters the header.

Under alloperating conditions the return or 15 imcerilcgs of the'wicksserve an additional purpose to that described in conveying portions ofthe liquid occasionally splashed on the plate 21 to-theinterior of thefloat. Such a portion may form in a film on the plate and engage the top20 of a wick 27, whereupon it drains slowly intothe float. Inthis caseeach wick acts as a tortuous return :d-uc-t wherein 'thegravitationalflow of such liquid portion 'is sufliciently :slow to permit andimproved herein, and it will therefore be "understood that I contemplatethe application of the principles of the invention in forms in whichsuch valve controlis not included, and that various other modificationsmay be resorted to as may suggest themselves to those skilled in theart.

1. In a refrigerating'apparatus comprising an i evaporator having inletmeans for admitting 40 lubricant and refrigerant for separation bygravity therein, lubricant return means comprisinga closed cup in theevaporator having a top portion extending above the liquid, said topportionhaving an aperture therein, a wick entering 15 the cup throughtheaper'ture of the top' portion thereof and having a portion extendinginto'the flu'bricant, said top portion being adapted to re- .an outletconduit extendingfrom the cavity of thecup toaportion exterior of theevaporator.

. '2. In a refrigerating apparatus comprising an evaporator having inletmeans for admitting lubricant and refrigerant for separation by"gravitytherein, lubricant return meanscomprising a cup therein havingvan opening in its top,

means closing said. opening, said 'means comprising a labyrinthstructure adapted to gravita- .tionally convey lubricant into said cupto permit gas to the outlet conduit, and means on thefioat 4 forconducting lubricant from the evaporator to the interior of the float.

4. In a refrigerating apparatus comprising an evaporator having an inletfor admitting lubricant and refrigerant for separation by gravitytherein, a control valve for said inlet, lubricant return meanscomprising an open float positioned within the evaporator for operatingsaid valve, an outlet conduit extending into the float, a cover for saidfloat, passage means in the cover to admit gas to the outlet conduit,and wick means extending into the float and having a portion enteringthe lubricant, said wick means being maintained in the lubricant by thebuoying movement of the float.

5. In a refrigerating apparatus comprising an evaporator having an inletfor admitting lubricant and refrigerant for separation by gravitytherein, a control valve for said inlet, lubricant return meanscomprising an open float positioned within the evaporator for operatingsaid'valve,

an outlet conduit extending into the float, a cover for said float,passage means in the cover to admit gas to the outlet conduit,cooperating flange means on the float and cover for retaining the coverin assembled relation, and means on the float for conducting lubricantfrom the evaporator to the interior of the float.

6. In a refrigerating apparatus comprising an evaporator provided withmeans for admitting refrigerant and lubricant admixed therewith, an openfloat for controlling the liquid admission means, an outlet conduitextending into the cavity of the float, lubricant return meanscomprising a cover for the float, and means for conveying liquiddeposited on the cover to the interior of the float, comprising alabyrinth structure entering the float through the cover and adapted toslowly convey lubricant into said cup to permit the evaporation ofrefrigerant carried therewith during transit.

JOSEPH ASKIN.

